From patchwork Tue Aug 30 01:16:38 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zack Weinberg X-Patchwork-Id: 15049 Received: (qmail 23727 invoked by alias); 30 Aug 2016 01:16:52 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 23513 invoked by uid 89); 30 Aug 2016 01:16:51 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-3.3 required=5.0 tests=AWL, BAYES_00, RP_MATCHES_RCVD, SPF_PASS autolearn=ham version=3.3.2 spammy=nest, reveals, originating, surgery X-HELO: mailbackend.panix.com From: Zack Weinberg To: libc-alpha@sourceware.org Cc: joseph@codesourcery.com Subject: [PATCH 06/13] Installed header hygiene (BZ#20366): Macros used in #if without checking whether they are defined. Date: Mon, 29 Aug 2016 21:16:38 -0400 Message-Id: <20160830011645.25769-7-zackw@panix.com> In-Reply-To: <20160830011645.25769-6-zackw@panix.com> References: <20160830011645.25769-1-zackw@panix.com> <20160830011645.25769-2-zackw@panix.com> <20160830011645.25769-3-zackw@panix.com> <20160830011645.25769-4-zackw@panix.com> <20160830011645.25769-5-zackw@panix.com> <20160830011645.25769-6-zackw@panix.com> MIME-Version: 1.0 sysdeps/unix/sysv/linux/bits/socket.h wants to know whether __flexarr will produce a real flexible array member -- specifically, one that doesn't alter sizeof(the structure containing it). Rather than make its approximation to that condition any more complicated, I added a new macro to sys/cdefs.h, __flexarr_is_fake, which reveals exactly what it wants to know. I also took the opportunity to flatten the rather messy conditional nest defining __flexarr. It seems to me that _LIBC should not appear in installed headers, but avoiding that for argp specifically would require more surgery than feels appropriate for this patch set. It's possible that "#ifdef _LIBC" would be sufficient, but I wanted to be conservative. * argp/argp.h: Check whether _LIBC is defined before expanding it. * posix/glob.h: Check whether __USE_XOPEN2K8 is defined instead of expanding it. * misc/sys/cdefs.h: Tidy up conditional nest defining __flexarr. Define __flexarr_is_fake when the compiler does not support flexible array members. * sysdeps/unix/sysv/linux/bits/socket.h: Use __flexarr_is_fake in definitions of struct cmsghdr and CMSG_DATA. --- argp/argp.h | 4 ++-- misc/sys/cdefs.h | 27 +++++++++++++++------------ posix/glob.h | 2 +- sysdeps/unix/sysv/linux/bits/socket.h | 4 ++-- 4 files changed, 20 insertions(+), 17 deletions(-) diff --git a/argp/argp.h b/argp/argp.h index 7cb5a69..5066776 100644 --- a/argp/argp.h +++ b/argp/argp.h @@ -511,7 +511,7 @@ extern void *__argp_input (const struct argp *__restrict __argp, #ifdef __USE_EXTERN_INLINES -# if !_LIBC +# if !(defined _LIBC && _LIBC) # define __argp_usage argp_usage # define __argp_state_help argp_state_help # define __option_is_short _option_is_short @@ -546,7 +546,7 @@ __NTH (__option_is_end (const struct argp_option *__opt)) return !__opt->key && !__opt->name && !__opt->doc && !__opt->group; } -# if !_LIBC +# if !(defined _LIBC && _LIBC) # undef __argp_usage # undef __argp_state_help # undef __option_is_short diff --git a/misc/sys/cdefs.h b/misc/sys/cdefs.h index 6e9b840..a6ba860 100644 --- a/misc/sys/cdefs.h +++ b/misc/sys/cdefs.h @@ -153,21 +153,24 @@ # define __errordecl(name, msg) extern void name (void) #endif -/* Support for flexible arrays. */ -#if __GNUC_PREREQ (2,97) -/* GCC 2.97 supports C99 flexible array members. */ +/* Support for flexible arrays. + Headers that should use flexible arrays only if they're "real" + (e.g. only if they won't affect sizeof()) should test + #ifndef __flexarr_is_fake. */ +#if defined __STDC_VERSION__ && __STDC_VERSION__ >= 199901L # define __flexarr [] +#elif __GNUC_PREREQ (2,97) +/* GCC 2.97 supports C99 flexible array members as an extension, + even when in C89 mode or compiling C++ (any version). */ +# define __flexarr [] +#elif defined __GNUC__ +/* Pre-2.97 GCC did not support C99 flexible arrays but did have + an equivalent extension with slightly different notation. */ +# define __flexarr [0] #else -# ifdef __GNUC__ -# define __flexarr [0] -# else -# if defined __STDC_VERSION__ && __STDC_VERSION__ >= 199901L -# define __flexarr [] -# else /* Some other non-C99 compiler. Approximate with [1]. */ -# define __flexarr [1] -# endif -# endif +# define __flexarr [1] +# define __flexarr_is_fake 1 #endif diff --git a/posix/glob.h b/posix/glob.h index e4548f6..ae70fa7 100644 --- a/posix/glob.h +++ b/posix/glob.h @@ -25,7 +25,7 @@ __BEGIN_DECLS /* We need `size_t' for the following definitions. */ #ifndef __size_t typedef __SIZE_TYPE__ __size_t; -# if defined __USE_XOPEN || __USE_XOPEN2K8 +# if defined __USE_XOPEN || defined __USE_XOPEN2K8 typedef __SIZE_TYPE__ size_t; # endif #else diff --git a/sysdeps/unix/sysv/linux/bits/socket.h b/sysdeps/unix/sysv/linux/bits/socket.h index 2266047..3b57101 100644 --- a/sysdeps/unix/sysv/linux/bits/socket.h +++ b/sysdeps/unix/sysv/linux/bits/socket.h @@ -273,13 +273,13 @@ struct cmsghdr with this. */ int cmsg_level; /* Originating protocol. */ int cmsg_type; /* Protocol specific type. */ -#if (!defined __STRICT_ANSI__ && __GNUC__ >= 2) || __STDC_VERSION__ >= 199901L +#ifndef __flexarr_is_fake __extension__ unsigned char __cmsg_data __flexarr; /* Ancillary data. */ #endif }; /* Ancillary data object manipulation macros. */ -#if (!defined __STRICT_ANSI__ && __GNUC__ >= 2) || __STDC_VERSION__ >= 199901L +#ifndef __flexarr_is_fake # define CMSG_DATA(cmsg) ((cmsg)->__cmsg_data) #else # define CMSG_DATA(cmsg) ((unsigned char *) ((struct cmsghdr *) (cmsg) + 1))